This section provides background information related to the present disclosure, which is not necessarily the conventional art.
With development of communication technology, research on vertical beamforming/FD MIMO (Full-Dimension Multiple-Input Multiple-Output) in LTE (Long Term Evolution) is started. The difference between the vertical beamforming/FD MIMO and the conventional transmission system lies in introducing a vertical dimension and using more antennas.
Moreover, with introduction of the vertical dimension, 2D antenna array is further proposed. Additionally, for convenience of description of large-scale antenna, a concept of TXRU (transceiver unit) is proposed correspondingly. TXRU is a radio transceiver unit with independent phase and amplitude.
There are multiple combinations of antenna arrays in 3D MIMO system. Moreover, the number of the TXRUs is variable, and a same number of TXRU corresponds different antenna configurations. Different antenna configurations result in different features of physical channels, in this case, the base station should select different codebooks to reflect the feature of the physical channels. In addition, different antenna configurations may affect a manner of transmitting a reference signal by a base station and a manner of a UE (User Equipment) measuring and feeding back the feature of a wireless channel. Hence, in order to improve transmission efficiency, it is necessary to notify the antenna configuration of the base station to the UE.
In a 3D MIMO system, an original notification unit for 1D antenna array information is no longer applicable since a 2D wireless array is used.
Hence, it is necessary to provide a new base-station-to-UE antenna configuration transmission design to serve for the 2D antenna array and the 3D MIMO system.